Never heard of that.  For what?

What is a "randomly generated Subscriber Number"? Where did you see that term? Who or what is asking you for it?

I concur w/ the last 2 replies I read 3 minutes ago, i.e. I also don't recognize the term "randomly generated Subscriber Number" related to using TurboTax, and I've been using TurboTax software since 2009, minimum!